/Engine/Source/Developer/SkeletalMeshUtilitiesCommon/Public/LODUtilities.h
This function apply the skinning weights from the saved imported skinning weight data to the destination skeletal mesh. The Destination will receive the weights has the alternate weights.
static bool UpdateAlternateSkinWeights ( [USkeletalMesh](API\Runtime\Engine\Engine\USkeletalMesh) * SkeletalMeshDest, const [FName](API\Runtime\Core\UObject\FName) & ProfileNameDest, int32 LODIndexDest, const [IMeshUtilities::MeshBuildOptions](API\Developer\MeshUtilities\IMeshUtilities\MeshBuildOptions) & Options )